The present invention relates to improvements in water hydrants and the like, such as those used in the art of snow-making for supplying water under high pressure to a snow-making device which acts to combine such water with compressed air to produce man-made snow. More particularly, this invention relates to apparatus for motorizing the opening and closing of a valve seat in such hydrants to control the flow of fluid therethrough.
In the commonly assigned U.S. patent application referenced above, there is disclosed an automated snow-making system which includes a remote-controlled circuit for controlling the opening and closing of valves in compressed air and water hydrants. By controlling the relative proportion of compressed air and water supplied to a snow-making device or "snow-gun", the snow quality (moisture content) can be adjusted to achieve a desired result at ski centers and resorts. In the system disclosed, the control circuit operates a bi-directional motor having a drive shaft operatively coupled to the valve stem of a water hydrant. As the drive shaft rotates, it rotates the valve stem of the hydrant through a high gear-reduction gear box. Rotation of the valve stem in conventional hydrants causes axial movement of the stem and of a plug to which the stem is connected. The plug cooperates with a valve seat to control fluid-flow through the valve seat.
In many hydrants of the above type, a substantial axial displacement of the valve stem is required in order to move the plug between a position in which it fully closes the valve seat, and a position in which it allows uninhibited flow of fluid through the seat. In the hydrant disclosed in the above-referenced application, such displacement amounts to about 2 to 3 centimeters. When a motor is used to effect rotation of the valve stem, some accommodation must be made to compensate for the axial movement of the end of the valve stem toward and away from the end of the motor shaft. While complex stem/shaft couplings (e.g., rack end pinion arrangements) have been considered to provide this accommodation, such couplings may be difficult and, hence, costly to fabricate.